Rotary charging devices using a chute for circumferential and radial distribution of the charge material have been known for several decades, mainly thanks to the present Applicant who brought the BELL LESS TOP® to industry in the early 1970s.
Such a rotary charging device is e.g. described in U.S. Pat. No. 3,693,812. It comprises a suspension rotor and a chute adjustment rotor that are supported in a stationary housing so as to be rotatable about a substantially vertical rotation axis. The chute is suspended to the suspension rotor so that it rotates with the latter for circumferential distribution of charge material. Furthermore, the chute is suspended to be pivotally adjustable about a substantially horizontal axis for radial distribution of charge material. The suspension rotor and the adjustment rotor are driven by a differential drive unit that is equipped with a main rotation drive, namely an electric motor, and an adjustment drive, namely an electric motor. The latter allows creating differential rotation between the suspension rotor and the adjustment rotor. A pivoting mechanism is provided for angular adjustment of the chute. This mechanism, which is connected to the chute and actuated by the rotor, transforms a variation in angular displacement between the suspension rotor and the adjustment rotor due to differential rotation, into a variation of the pivotal position i.e. the tilt angle of the chute.
The rotary charging device of U.S. Pat. No. 3,693,812 is further equipped with a drive unit for driving the two rotors. This unit is enclosed in a casing arranged on the stationary housing that supports the rotors and the chute. The casing has a primary input shaft; a secondary input shaft; a first output shaft, hereinafter called rotation shaft; and a second output shaft, hereinafter called adjustment shaft. The primary input shaft is driven by the main rotation drive. Inside the casing, a reduction mechanism connects the primary input shaft to the rotation shaft, which extends vertically inside the stationary housing where it is provided with a gearwheel that meshes with a gear ring of the suspension rotor. The adjustment shaft also extends vertically into the stationary housing where it is provided with a gearwheel that meshes with a gear ring of the adjustment rotor. Inside the casing of the drive unit, the rotation shaft and the adjustment shaft are interconnected by means of an epicyclic differential mechanism, i.e. a sun-and-planet gear train. The latter mainly comprises a horizontal annulus (ring gear) that has external teeth meshing with a gearwheel on the rotation shaft; a sun gear that is connected to the secondary input shaft; at least two planet gears that mesh with internal teeth of the annulus and with the sun gear. This sun-and-planet gear train is dimensioned so that the rotation shaft and the adjustment shaft have the same rotational speed imparted by the main rotation drive when the secondary input shaft is stationary, i.e. when the adjustment drive is at stop. The adjustment drive is a reversible drive and connected to the secondary input shaft. By virtue of the differential mechanism, the adjustment drive allows driving the adjustment shaft at a faster and at a lower rotational speed than the rotation shaft to thereby produce a relative i.e. differential rotation between the suspension rotor and the adjustment rotor. The pivoting mechanism transforms such differential rotation into pivoting motion of the chute.
Such rotary charging device with distribution chute has proven very successful in industry and various manufacturers have developed their own versions. In the majority of designs, the drive motors, drive unit, the rotation shaft and adjustment shaft are arranged vertically, generally on the top of the stationary housing. As described above, the rotation drive may be achieved relatively easily by a pinion engaging a ring gear attached to the supporting rotor. The tilting drive is more complex as the torque provided by the vertical electric motor has to be converted in such a way to be able to pivot the distribution chute about the horizontal axis. In this regard, the design of the tilting mechanism has led to many developments, using connecting rods, cables, or hydraulic cylinders and specially designed gears. In particular, the tilting drive unit described above is a key component of the device for distributing charge material. Since it is custom made, it represents a significant part of the total cost of the device. Moreover, in order to ensure continuous operation of the furnace when the drive unit requires servicing or major repair, a complete spare unit is typically kept in stock by the furnace operator.
Over the years, the motivations that lead to the development of new designs where:                improving the compactness of the device, in particular for small/medium blast furnace installations;        improving the reliability of the rotary and tilting drive mechanisms;        facilitating the access to the stationary housing, which may be difficult complicated by the various external casings mounted thereto;        reducing the quantity of casing openings (seals, gaskets . . . );        improving the reliability of the rotary and tilting drive mechanisms.        
In EP 0 863 215 it has been proposed to actuate the chute by means of an electrical motor arranged on the rotating part (suspension rotor) that supports the chute. This solution eliminates the need for a highly developed mechanical gear arrangement for varying the chute inclination. It does however require means for electric energy transfer, from the stationary part to the rotatable part, in order to power the electric motor on the chute-supporting rotor.
The solution provided in EP 0 863 215 seems however unfinished and inappropriate for practical use to face the harsh industrial condition, with substantial dust and heat. The power supply to the tilting drive is another problem, not addressed therein.